2.2 Chapter 12 Questions
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Macomb Community College *
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2100
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Industrial Engineering
Date
Dec 6, 2023
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3
Uploaded by CountRaven3911
2.2 Chapter 12 Questions
1. What options are available when selecting an assembly method?
Manual, Automatic,
and Robotic
2. What are the major characteristics of each of the available assembly methods?
Manual
: The operations are usually carried out manually with or without the aid of
simple, general-purpose tools like screw drivers and pliers.
Automatic / Fixed Automation
: (also sometimes called the Detroit type) either
synchronous indexing machines and automatic feeders. This system is usually to
assemble only one specific product.
Robotic
: Can be in multiple forms, the first being a one arm general purpose robot
operating at a single workstation that includes parts, feeders, magazines and so on.
3. Discuss some of the factors that affect the selection of an appropriate assembly
method.
The cost of assembly, the annual production volume (or production rate), the
number of individual components to be assembled in a product, the number of different
versions of a product, or products, the availability of labor at a reasonable cost, and the
payback period.
4. Define the term
design for assembly
.
Simplifying the products structure by reducing
the number of components and minimizing the number of assembly operations required.
The aim is to make the manufacturing process easier.
5. What are the benefits of applying the concept of design for assembly?
To optimize
proper assembly and correct functioning, to reduce wastage of parts, and allow a higher
degree of reliability and operational efficiency.
6. What has always been the traditional approach for DFA?
7. What three questions form the criteria for eliminating a part from an assembly or
combining it with its neighboring part?
a.) Does the part move relative to all other parts already assembled?
b.) Must the part be of a different material or be isolated from other parts already
assembled? (Only fundamental reasons concerned with material properties are
acceptable.)
c.) Must the part be separate from all other parts already assembled because otherwise
necessary assembly or disassembly of other parts would be impossible?
8. List the guidelines for product design for manual assembly.
- Eliminate the need for any decision making by the assembly worker, including his or
her having to make any final adjustments.
- Ensure accessibility and visibility.
- Eliminate the need for assembly tools or special gauges by designing the individual
components to be self-aligning and self-locating.
- Minimize the types of parts by adopting the concept of standardization as a design
philosophy.
- Minimize the number of individual parts in an assembly by eliminating excess parts
and, whenever possible, integrating two or more parts together.
9. What is the ideal insertion motion? Why?
The use of vertical insertion (along the Z-
axis) is ideal, this uses the advantages of gravity.
10. Why should you try to avoid reorienting parts during assembly?
They are considered
wasteful motions and result in increased assembly time and cost.
11. What effect does the concept of standardization of parts have on the assembly
process?
The concept of standardization of parts works towards improving operational
readiness and reducing lifestyle costs.
12. Does nesting (or tangling) of parts while in the bulk have any effect on the assembly
operation?
Yes, and this can be avoided by making simple modifications in the design
and eliminating the use of fragile or brittle materials like cables and cords.
13. Why should parts be symmetrical?
Facilitates easy orientation and handling during
assembly.
14. What is your advice if you cannot get the parts to be symmetrical?
The alternative is
to design for asymmetry that is easily recognizable by the assembly worker.
15. List the guidelines for product design for automatic assembly.
- Reduce the number of different components in an assembly by using the three
questions listed previously in the design guidelines for manual assembly.
- Use self-aligning and self-locating features in parts to facilitate the process of their
assembly.
16. How can the use of self-aligning and self-locating features facilitate automatic
assembly?
The use of chamfers, guide pins, dimples, molded in locators, and certain
types of screws.
17. Can screws be considered as essential parts in a product? Why?
No, it is usually
recommended to avoid fastening together by screws because it is expensive and time
consuming.
18. What is the ideal fixturing method in automatic assembly?
Flexible fixturing. This is
where a single work holding system may be employed to hold workpieces of various
shapes and sizes.
19. Discuss the concept of feedability.
This concept involves quantitative estimation of
the odds of feeding a part having certain geometric characteristics to the assembly
station in a specific orientation.
20. Why should parts with a low center of gravity be favored in automatic assembly?
The part will have a natural tendency to be fed in one particular direction. Also, when
the part is transferred onto a conveyor belt, it will not tip or be disoriented due to the
force of inertia.
21. List two rules for product design for robotic assembly.
- Design a component so that it can be grasped, oriented, and inserted by that robots
end effector.
- Design parts so that they can be presented to the robots arm in an orientation
appropriate for grasping. Also, eliminate the need for reorienting assemblies (or
subassemblies) during the assembly operation.
22. What are the methods for performing DFA analysis?
- Functional Analysis
- Feeding Analysis
- Fitting Analysis
23. List some of the advantages, characteristics, features, and limitations of each DFA
analysis method.
Functional Analysis
: Components are divided into two groups. The first group includes
components that perform a primary function (group A). The second group involves
nonessential components that perform only secondary functions like fastening and
locating (group B). Design efficiency is the product of dividing the number of essential
parts by the total number of parts and can be given by the following equation.
Design Efficiency = A / (A+B) x 100
The target objective is to achieve a design efficiency of 60 percent.
Feeding Analysis
: Concerned with the problems associated with handling components
(and subassemblies) until they are admitted to the assembly system. The feeding /
handling ratio can be calculated with this equation.
Feeding / Handling ratio =
𝐹???𝑖??
𝐻????𝑖?? 𝑖???𝑥
𝑁????? ?? ??????𝑖?? ??????????
An ideal value for this ratio and one that is often taken as a target goal is 2.5.
Fitting Analysis
: Divided into a number of subsystems, including gripping, insertion,
and fixing analyses. An index is given to each part based on its fixing requirements,
resistance to insertion, and whether or not there will be restricted vision during
assembly. The fitting index is manipulated to yield the fitting ratio as given by the
following equation.
Fitting ratio = fitting index / number of essential components
The value of the fitting ratio should be around 2.5
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